// 隐式丢失：
function sayHi3() {
    console.log('Hello,', this.name);
}
var person3 = {
    name: 'YvetteLau',
    sayHi: sayHi3
}
var name = 'Wiliam';
var Hi = person3.sayHi;
Hi(); // this 找到全局的name 'Wiliam' ,因为在node环境下才为undefind